This invention relates to the isolated laevorotatory isomer of 2-benzoyl-4-oxo-1,2,3,6,7,11b-hexahydro-4H-pyrazino[2,1-a]isoquinoline (Compound A), which exhibits excellent and unexpectedly high anthelmintic activity.
In the literature and in practice, several compounds are known which are effective against one or more tapeworm (cestode) types, for example, niclosamide [N-(2-chloro-4-nitrophenyl)-5-chlorosalicylamide], quinacrine [2-methoxy-6-chloro-9-[(1-methyl-4-diethylaminobutyl)-amino]-acridine], dichlorophene(2,2' -dihydroxy-5,5'-dichlorodiphenylmethane).
These agents, however, are in part ineffective against the larval forms of the cestodes, as well as against those adult tapeworms which are not located in the intestinal lumen. Also, the echinococci, e.g., Echinococcus granulosus, have been difficult to combat heretofore and the results have not always been completely satisfactory. Additionally, with several of these agents, e.g., quinacrine and dichlorophene, considerable undesired side effects, e.g., vomiting, nausea, can be expected.
It is possible to utilize other compounds for the combatting of schistosomes, for example antimony-containing agents, e.g., stibophen [sodium antimony bis(pyrocatechol-2,4-disulfonate)], niridazole [1-(5-nitro-2-thiazolyl)-imidazolidin-2-one], lucanthone [1-(2-diethylaminoethylamino)-4-methylthiaxanthone hydrochloride], etc. However, all these known compounds are not optimally effective against the various forms of schistosomiasis, so that they can be utilized without problems, e.g., mass treatment of whole populations.
The anthelmintic properties of Compound A exceed to a surprisingly degree those of the racemic 2-benzoyl-4-oxo-1,2,3,6,7,11b-hexahydro-4H-pyrazino[2,1-a]isoquinoline (Compound B), which is the subject of Application Ser. No. 449,690, filed Mar. 11, 1974.